Fig. 9.

Macrophages in alveolar walls and alveolar spaces. Confocal images of sections through alveolar parenchyma of COVID 6, 8, and 1. The dashed squares in the images on the left are magnified on the right. The extracellular matrix in the alveolar walls emits a weak fuchsia autofluorescent signal. DAPI served as nuclear stain. (a–d) In COVID 6 and COVID 8, groups of CD68-immunoreactive macrophages are observed in close relation to the alveolar walls. (a,c) The CD68-immunoreactive signal is prominent but does not completely fill the alveolar spaces. (b,d) Macrophages harbour clusters and aggregates of N puncta in areas indicated with a stippled line. (b) S-sense puncta are not observed and reflect the absence of viral replication in macrophages. (e,f) In COVID 1, alveolar spaces are filled with CD68-immunoreactive macrophages. (e) KRT8-immunoreactive signal labels pneumocytes that line the alveolar walls. (f) Macrophages in the alveolar spaces harbour N puncta in areas indicated with a stippled line. The names of RNAscope probes are in italics and the names of antigens/proteins that are revealed as immunoreactive signal by antibodies are in roman.